A. Field of the Invention
This invention relates to a trench raceway of the type useable for access flooring for computer rooms and office buildings. More particularly, this invention relates to a trench raceway that is held in place by pedestals adjacent the access floor above a subsurface or subfloor.
B. State of the Art
Computer rooms have long utilized a type of raised flooring to provide the type of electrical security and adaptability of wiring schemes required for sensitive computer equipment. The space between the access floor and the subfloor provides a large, electrically isolated, secure, and relatively easily accessible area for routing, adjusting, and rerouting of computer cable, conduit and other ducting under the access floor. Since computers can be highly sensitive to electrical interference and are often being moved, upgraded, maintained, and changed in the room, such access floors have long been an important aspect of computer room design and construction in many buildings.
One common structure for access floor consists of adjacent rectangular access floor panels suspended above the subfloor by means of a series of adjustable pedestals with planar upper and lower ends. The lower end rests on the subfloor and the upper end supports the bottom sides of an adjacent access floor panels. Removal of an access panel exposes portions of the supporting pedestals for that panel as well as the space under that access floor panel and above the portion of the subfloor below it.
Office buildings having access flooring require wiring paths not only for low voltage computer lines but also for the more traditional types of wiring such as low voltage phone lines and higher voltage power lines. The power lines, in particular, must pass through conduits, ducts, or raceways that are electrically isolated from the computer cables or ducting running within the access area between the access flooring and the subfloor.
One solution has used surface metal raceways above the access flooring, on the upper surface of the flooring itself or along walls in the room. Surface metal raceways are unattractive and can trip persons if located along the flooring itself. They do not hide the raceways as is common and often expected by the tenant, interior designers, etc. They are also typically only light duty solutions and generally do not have significant wire carrying capacity. Indeed, the National Electrical Code limits them to being 20% filled with wiring.
Another solution has been the utilization of the traditional underfloor raceway in the concrete subfloor. Just as in traditional concrete flooring without access flooring above it, this type of raceway is rectangular with access covers over junction boxes set in a depression in the concrete floor so that the covers can be removably secured to the junction boxes, thus providing an accessible wireway passage within the raceway. The raceway can contain internal partitions for maintaining electrical separation of various types of wires (e.g., phone versus power lines) within the raceway.
Since this type of underfloor raceway is located in the subfloor, it is located well below the access floor. In order to access this type of underfloor raceway, the user must: (1) remove a section of the access floor; (2) check to see if the desired raceway is located beneath the flooring; (3) when the desired raceway is discovered, reach through the opening, clear any computer wiring in the way, and then remove the raceway cover and set it aside; and then (4) have to work within the raceway in the subfloor under and separated from the access opening in the access floor.
This underfloor raceway and accessing procedure can be cumbersome, difficult, and time consuming. It also cannot be utilized when an access floor is to be installed above a concrete floor not having a suitable underfloor raceway already pre-installed in the concrete. Even when the concrete subfloor contains pre-existing underfloor raceways with the desired capacity, the location of the raceways may be less than desired at the time the access floor is installed or at some later time when the arrangement of the computers, etc., may be changed in a manner rendering a prior raceway path undesirable.
Other solutions have involved cable trays, metal wireways (conduits), or other ducts installed below the access floor. Often, low voltage wiring (such as computer wiring) may run over or under electrical conduits or ducts at unspecified angles, making routing and location of cables extremely unmanageable. In addition, conduits and other ducts result in additional loading and an increase in height of the access floor, which increases the height of the building. Combined with the weight of the access panel (approximately 10 lbs. per square foot) wireways and ducts can significantly increase the size of the structural framing. This can significantly increase the cost of building the access floor and the building containing the access flooring.
In addition, metal wireways are only useable for exposed electrical work according to the National Electrical Code. They are thus not acceptable under the Code for use in access flooring.